I have installed LO 4.3 on XP but it fails to run, reporting a fatal error.
Extension manager: exception in synchonize.
This is a freshly installed XP Pro SP3, up to date with patches, on an old machine with 1G RAM and a single core Athlon processor.
Other stuff (FFox, Audacity and so on) works just fine.
First I would reset the user profile following the procedure described in: https://wiki.documentfoundation.org/UserProfile
If not successful I would uninstall LibO and remove any traces (see application folder in XP).
Next I would download LibO from: http://www.libreoffice.org/ and make a new installation.
I have currently the LibO v 4.2.6.3 installed on an XP machine and used several times portable version of Lib 4.3 on the same machine without any problem.
Thank you for responding
I renamed %appdata%\LibreOffice\4 and LO generates a new folder with, as far as I can see, all the correct bits in it, and then throws the exception.
I couldn’t find a checksum for the LO 4.3.2.2 so I have downloladad another copy and checksums for the two files match.
I have completely removed and then re-installed LO.
The problem remains unchanged 
This really is a strange situation. ---- Did you download from http://www.libreoffice.org/ ? — Please describe step by step how you did the installation. The best is to repeat the installation and make notes for each step and setting you made including the results/reactions/ messages of the PC.
Not sure how much detail is appropriate.